Welcome

Dr Andrea Banzatti - Postdoctoral Research Associate at LPL

Ph.D., 2013, ETH Zurich (Advisor: Prof. Michael R. Meyer)

Click here for my publications on ADS and ADS beta , and for my CV (short version)

Who am I, and what do I do?

I am an observational astronomer, but I do not look at images of stars, as I’m often asked. I work in a field of less immediate grasp, one that I initially disregarded, and that I now love with all my heart: spectroscopy. Ask astronomers what’s the one most essential thing they need in their research, and they will tell you “light, of course!”. With spectroscopy, we let the light collected with telescopes reveal all its secrets, hidden in the “wiggles” that atoms and molecules in the Universe imprint in it. With this technique, I have the honor and joy to study and discover aspects of the birth of exoplanets in protoplanetary disks. Below, you find details on my research as well as some examples of my teaching and outreach activities. If you would like to know more, please do not hesitate to contact me!

NEWS:

A new episode in the inner disk evolution "saga": Observing the linked depletion of dust and CO gas at 0.1-10 au in disks of intermediate-mass stars

My new work on The depletion of water during dispersal of planet-forming disk regions is now published on ApJ!

Talks and discussions from the 2016 workshop "Linking Exoplanet and Disk Compositions" are now available on the STScI webcast archive .

In October 2016 I moved from Space Telescope Science Institute to the University of Arizona, Lunar & Planetary Laboratory.

Using the method proposed in Banzatti et al. 2015 , a paper on Nature presents the first ALMA image of the water snow line in a protoplanetary disk.

Links:

Project EOS: Earths in Other Solar Systems

My post on the STScI Science Blog: "Disk, gaps, and exoplanets - a journey on the wings of a dragonfly"

My STScI Public Lecture on Building New Worlds in Protoplanetary Disks

Simon Bruderer's essential conversion tools (Thank you Simon!)

Science highlights

THE PHYSICAL AND THERMO-CHEMICAL EVOLUTION OF PLANET-FORMING DISKS AT 0.01-10 AU

The top figure shows the temperature-radius (T-R) diagram of carbon monoxide (CO) gas in protoplanetary disks (Banzatti & Pontoppidan 2015). The bottom figure shows representative water and CO spectra from a large survey combining Spitzer-IRS and VLT-CRIRES observations (Banzatti et al. 2017). CO is a ubiquitous tracer of molecular gas in disks, and a sensitive thermometer of the radiation environment. The diagram above is constructed from spectroscopy surveys of rovibrational CO emission obtained with CRIRES at the Very Large Telescope, which currently provides the sharpest and most sensitive view of molecular gas in inner disks. The diagram unveils an empirical temperature profile for inner disks around solar-mass stars between 0.03 and 3 AU, by tracing the local warm dust color through infrared pumping. Between 2 and 25 AU, an inversion in the temperature profile reveals disks that have large depletions in their inner dust and gas radial structures, allowing ultraviolet pumping of CO emission at such large distances from the central stars. The T-R diagram of CO emission provides an empirical sequence of disk gap opening in protoplanetary disks, spanning the entire planet-formation region (~ 0.1-10 AU) and evolutionary stages from primordial to debris disks. In the figure above, the CO sequence is put into context of the Solar System planets and of the observed distribution of massive exoplanets that may migrate and open gaps in disks (with Msini > 0.5 Jupiter masses, from exoplanets.org).

Read here the scientific publication of these works, in the Astrophysical Journal: Banzatti & Pontoppidan 2015 and Banzatti et al. 2017a.

Read here a more poetic description in the STScI science blog: "Disk, gaps, and exoplanets - a journey on the wings of a dragonfly"

This work is now becoming a real saga! After the first two papers described above, a third paper demonstrates that the CO sequence displayed in the top figure is tracing the depletion of dust at planet-forming radii, in the disks of Herbig stars: Banzatti et al. 2017b (figure here above). And more is coming on the analysis of molecular gaps and holes in inner disks at 0.01-10 au, including modeling work and synergies with studies of inner disk winds, stay tuned...

Imaging the WATER SNOW LINE from two ALMA continuum bands

The figure illustrates a proof-of-concept method proposed in Banzatti, Pinilla, et al. 2015 to image the water snow line in protoplanetary disks, through its signature imprinted in the dust continuum spectral index as observed at millimeter wavelengths from two ALMA continuum bands. We adopt a physical disk model that includes dust coagulation, fragmentation, drift, and a change in fragmentation velocities of a factor of 10 between dry silicates and icy grains as found by laboratory work. We find that the presence of a water snow line leads to a sharp discontinuity in the radial profile of the dust emission spectral index due to replenishment of small grains through fragmentation. The cartoon to the left illustrates the key components of this effect, while the model simulation to the right shows how ALMA would image the snow line by combining two continuum bands. We propose that ALMA continuum images of disks should be found to commonly show the water snow line, when the necessary spatial resolution is achieved.

This work is now available in ApJ Letters: Banzatti, Pinilla, et al. 2015, ApJL, 815, L15

A first detection of the water snow line using this method has been reported by Cieza et al. 2016 using ALMA: the paper is published on Nature

Monitoring the EFFECTS OF EPISODIC ACCRETION outbursts: UV photo-chemistry and inner disk draining

The figure shows a summary of observations and results obtained as part of monitoring studies of EX Lupi (the prototype of EXor variables) pre-, during, and post-outburst in the years 2005-2014. The lightcurve of EX Lupi is shown at the top of the figure: the strong accretion outburst in 2008 is visible in the 5 magnitude increase in the V band, while the data utilized in this work are marked with vertical lines. The Spitzer-IRS spectra were obtained before and during the ouburst, showing disappearance of organics and simultaneous increase in water and OH emission during outburst. This dataset provides first direct evidence that UV photo-chemistry (dissociation of molecules, e.g. water into OH) is triggered in inner disk surfaces during accretion flares. The increase in water emission is consistent with a larger amount of water vapor as released by icy bodies evaporated through a recession of the snow line at larger disk radii during outburst. The CRIRES data showed a strong decrease in water, OH and CO emission after outburst, and allowed to measure the amount (> 1 order of magnitude) and region (< 0.3 AU) of disk material drained during the outburst, which left the inner disk largely depleted of gas. Now the system is again in an "accumulation" phase (cartoon at the bottom), during which disk gas is piling up beyond the corotation radius until the next outburst will be triggered. Observations of EX Lupi give now the opportunity to study the timescales of organic chemistry in inner disks, through monitoring their infrared features while organics may re-form after UV photo-dissociation.

Read here the scientific publications of this study, on the Astrophysical Journal Letters: Banzatti et al. 2015, ApJL, 798, 16 , and on the Astrophysical Journal: Banzatti et al. 2012, ApJ, 745, 90

Teaching & Outreach

Explaining astronomy to students and the public is one of the best opportunities we have as scientists to reflect on what seems obvious to us, re-think it under different eyes, and deeply enjoy its re-discovery. This is why I constantly search for opportunities to meet students and the public, whenever my research schedule allows that, to teach and to share the adventure that astronomy and scientific research are for all of us. I have seen this adventure becoming attractive for tens of people regardless of age and backgrounds. It is this joy that keeps me eager to go back to the classroom and to outreach activities, and to keep improving as a teacher and communicator.

Observational astronomy for undergraduates

As a teaching assistant at the ETH in Zurich, I served for three semesters at the “Astrowoche”, a week of observations in the Swiss Alps. Students used 8”-14” optical telescopes and a radio interferometer to perform various astronomical projects, including measurements of Jupiter’s moons orbits (in the footsteps of Galileo!) and of the Sun’s diameter. The students had the opportunity to follow the path of real astronomical observations, from preparation and strategical planning, to learning the instrumentation (telescopes, detectors, software), performing the observations, and presenting the results in a structured scientific report.

The power of active engagement

In one of the guest lectures I gave at UA, I surveyed the students to evaluate the effectiveness of my teaching methods. The course had been previously taught in a lecturing style with little student participation. I set up my lecture from the start as an investigation where, in group activities and live experiments, we would discover and learn together. In a little more than 1 hour, the students had two group activities and two live experiments that I designed for them, to see in action the key concepts of the lecture. The result was a success! The histogram illustrates the data from the anonymous questionnaires I gave to the students: by the end of the lecture, their interest increased by > 2 points for 60% of the students, including all the least interested ones!

Telescopes "behind the scenes"

It looks like a giant ice box, but its purpose is actually the opposite. I organized a tour for a dozen AU students to see a milestone at the Mirror Lab in Tucson, a spectacular event that occurs only once every 2.5 years! Chunks of glass are put into a giant spinning furnace, to be molten and shaped into the 5th of the 8-meter mirrors of the Giant Magellan Telescope. Only the purest glass in the world can be used to make this mirror at the needed perfection, a glass made in Japan. A unique opportunity for students, but also for professional astronomers, to see what happens "behind the scenes" in the most advanced next generation of telescopes.

Physics experiments and the adventure of scientific research

I had the joy to engage students in the adventure of scientific research also in advanced physics labs. Take for instance the experiment of thermionic emission. First, I introduced students to the scientific mystery behind the effect of the 1928 Nobel Prize in Physics: the emission of “thermions” from a heated metallic filament. Then I guided students to elaborate how to set up the instrumentation to measure currents as a function of temperature of a tungsten filament, and how to carefully obtain a difficult set of measurements (we had to sit in a dark room for hours, comparing colors of incandescent filaments through an eyepiece!). With the data obtained, the students had the opportunity to identify the regime of linearity of Richardson’s Law, and gain their own "Nobel Prize"! Science never grows old!

Outreach activities

Just whenever I have the opportunity, I love to spend time with kids, students, and adults with a telescope under a starry sky, inside the dome of a planetarium, or with a set of slides, a projector, and a good story to tell! I am passionate about sharing with people the exciting paths of scientific investigation and discovery, the history of astronomical observations from Galileo to the modern 8-m-class telescopes, and the most advanced research frontiers on the origins of planets. Time and again, in these events I learn from people how scientific research has its roots in a desire that we all share. A desire to understand, learn, and discover what’s beyond.

Interested in any of the above? Please feel free to contact me!

Exoplanets & Disks 2016

Linking Exoplanet and Disk Compositions - STScI workshop on September 12-14, 2016

Scientists gathered in this workshop to tackle some of the most compelling scientific questions on the origins of exoplanet diversity. Do exoplanet compositions retain the imprint of large-scale disk processes? Do disks include compositional trends that imprint on planets? What do we learn in this context from observations of Solar System bodies? And what can we test with observations of disks and exoplanets in the near future? Several round-table discussions during the workshop aimed at identifying long-lasting and observable links between exoplanet and disk compositions, to help the community in shaping ongoing modeling efforts as well as the essential parameter space to cover with existing and upcoming observatories for exoplanet and disk characterization. Talks and discussions from the workshop are now available on the STScI webcast archive .

Publications & Plots

Contact

Current address:

University of Arizona
Lunar and Planetary Laboratory
1629 E University Blvd
Tucson, AZ 85721
USA

Email:

banzatti-AT-lpl.arizona.edu